Evaporative Mass Transfer of Hydrophobic Organic Compounds From Exposed Contaminated Sediment and Dredged Materials.
Date of Award
Doctor of Philosophy (PhD)
Kalliat T. Valsaraj
Dredged sediment materials stored in confined disposal facilities (CDF) contain several hydrophobic organic compounds (HOC) such as polynuclear aromatic hydrocarbons (PAH), some of which are suspected carcinogens. The primary objective of this study was to evaluate the volatilization of HOCs from contaminated, exposed sediment dredged materials and contribute to the risk assessment framework being developed by the U.S. Army Corps of Engineers. Laboratory experiments were performed to measure HOC tracer emissions to air from contaminated sediments (laboratory inoculated and field aged) placed in a specially designed flux chamber. Flux was influenced by a number of factors such as relative humidity of the air in contact with the surface, sediment moisture content, sediment porosity and sediment oil and grease content. These factors affected the concentration of chemical available for transport in the pore air as a result of differences in sorptive retardation of the chemical to the sediment and contaminant diffusion. Reworking of sediments enhanced fluxes from field sediments due to exposure of fresh sediments to the air. Capping of exposed dredged material, with two materials clean sand and clean sediment, resulted in significant decrease of the tracer chemical emission. There was satisfactory agreement between experimental data and model prediction. The effect of shrinkage cracks, on the surface of exposed dredged material, on emission was evaluated using an empirical expression developed from existing water evaporation data from a simulated crack. Air emissions from resuspended sediments were measured using an oscillating grid flux chamber containing a bed of contaminated sediment. The fluxes to air were directly related to the suspended sediment concentration. The observations in laboratory studies were verified in a field experiment using a pilot scale CDF and the measured fluxes were in good agreement with model predicted fluxes. The measured emission flux of phenanthrene from the pilot CDF were used in an atmospheric dispersion model to assess human exposure risk.
Ravikrishna, Raghunathan, "Evaporative Mass Transfer of Hydrophobic Organic Compounds From Exposed Contaminated Sediment and Dredged Materials." (2000). LSU Historical Dissertations and Theses. 7329.